1
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Orr BO, Fetter RD, Davis GW. Activation and expansion of presynaptic signaling foci drives presynaptic homeostatic plasticity. Neuron 2022; 110:3743-3759.e6. [PMID: 36087584 PMCID: PMC9671843 DOI: 10.1016/j.neuron.2022.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 06/07/2022] [Accepted: 08/11/2022] [Indexed: 12/15/2022]
Abstract
Presynaptic homeostatic plasticity (PHP) adaptively regulates synaptic transmission in health and disease. Despite identification of numerous genes that are essential for PHP, we lack a dynamic framework to explain how PHP is initiated, potentiated, and limited to achieve precise control of vesicle fusion. Here, utilizing both mice and Drosophila, we demonstrate that PHP progresses through the assembly and physical expansion of presynaptic signaling foci where activated integrins biochemically converge with trans-synaptic Semaphorin2b/PlexinB signaling. Each component of the identified signaling complexes, including alpha/beta-integrin, Semaphorin2b, PlexinB, talin, and focal adhesion kinase (FAK), and their biochemical interactions, are essential for PHP. Complex integrity requires the Sema2b ligand and complex expansion includes a ∼2.5-fold expansion of active-zone associated puncta composed of the actin-binding protein talin. Finally, complex pre-expansion is sufficient to accelerate the rate and extent of PHP. A working model is proposed incorporating signal convergence with dynamic molecular assemblies that instruct PHP.
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Affiliation(s)
- Brian O Orr
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158 USA
| | - Richard D Fetter
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158 USA
| | - Graeme W Davis
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158 USA.
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2
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Ashdown GW, Williamson DJ, Soh GHM, Day N, Burn GL, Owen DM. Membrane lipid order of sub-synaptic T cell vesicles correlates with their dynamics and function. Traffic 2017; 19:29-35. [PMID: 28981993 DOI: 10.1111/tra.12532] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 10/03/2017] [Accepted: 10/03/2017] [Indexed: 01/22/2023]
Abstract
During an immune response, T cells survey antigen presenting cells for antigenic peptides via the formation of an interface known as an immunological synapse. Among the complex and dynamic biophysical phenomena occurring at this interface is the trafficking of sub-synaptic vesicles carrying a variety of proximal signalling molecules. Here, we show that rather than being a homogeneous population, these vesicles display a diversity of membrane lipid order profiles, as measured using the environmentally sensitive dye di-4-ANEPPDHQ and multi-spectral TIRF microscopy. Using live-cell imaging, vesicle tracking and a variety of small molecule drugs to manipulate components of the actin and tubulin cytoskeleton, we show that the membrane lipid order of these vesicles correlate with their dynamics. Furthermore, we show that the key proximal signalling molecule Linker for Activation of T cells (LAT) is enriched in specific vesicle populations as defined by their higher membrane order. These results imply that vesicle lipid order may represent a novel regulatory mechanism for the sorting and trafficking of signalling molecules at the immunological synapse, and, potentially, other cellular structures.
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Affiliation(s)
- George W Ashdown
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
| | - David J Williamson
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
| | - Gary H M Soh
- Friedrich Miescher Laboratory, University of Tübingen, Tübingen, Germany
| | - Nathan Day
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
| | - Garth L Burn
- Max-Planck Institute for Infection Biology, Berlin, Germany
| | - Dylan M Owen
- Department of Physics and Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
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3
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Wang J, Richards DA. The actin binding protein scinderin acts in PC12 cells to tether dense-core vesicles prior to secretion. Mol Cell Neurosci 2017; 85:12-18. [PMID: 28823945 DOI: 10.1016/j.mcn.2017.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 08/07/2017] [Accepted: 08/16/2017] [Indexed: 11/18/2022] Open
Abstract
Mechanistic understanding of the control of vesicle motion from within a secretory cell to the site of exocytosis remains incomplete. In this work, we have used total internal reflection (TIRF) microscopy to examine the mobility of secretory vesicles at the plasma membrane. Under resting conditions, we found vesicles showed little lateral mobility. Anchoring of vesicles in this membrane proximal compartment could be disrupted with latrunculin A, indicating an apparent actin dependent process. A candidate intermediary between vesicles and the actin skeleton is the actin binding protein scinderin. Co-transfection of an shRNA construct against scinderin blocked secretion, and also increased the mobility of vesicles in the membrane-proximal section of the cell, indicating a dual role for scinderin in secretion; tethering vesicles to the cytoskeleton, as well as liberating them following stimulation through the previously described calcium dependent actin severing activity. Analysis of lipid dependence indicates that scinderin exhibits calcium dependent binding to phosphatidyl-inositol monophosphate, providing a possible mechanism for vesicle binding.
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Affiliation(s)
- J Wang
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, MLC2001, 3333 Burnet Avenue, Cincinnati, OH 45229, United States
| | - D A Richards
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, MLC2001, 3333 Burnet Avenue, Cincinnati, OH 45229, United States; Department of Basic Pharmaceutical Sciences, Husson University School of Pharmacy, 1 College Circle, Bangor, ME 04401, United States.
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4
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Abstract
Exocytosis is the fundamental process by which cells communicate with each other. The events that lead up to the fusion of a vesicle loaded with chemical messenger with the cell membrane were the subject of a Nobel Prize in 2013. However, the processes occurring after the initial formation of a fusion pore are very much still in debate. The release of chemical messenger has traditionally been thought to occur through full distention of the vesicle membrane, hence assuming exocytosis to be all or none. In contrast to the all or none hypothesis, here we discuss the evidence that during exocytosis the vesicle-membrane pore opens to release only a portion of the transmitter content during exocytosis and then close again. This open and closed exocytosis is distinct from kiss-and-run exocytosis, in that it appears to be the main content released during regular exocytosis. The evidence for this partial release via open and closed exocytosis is presented considering primarily the quantitative evidence obtained with amperometry.
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5
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Spatiotemporal detection and analysis of exocytosis reveal fusion "hotspots" organized by the cytoskeleton in endocrine cells. Biophys J 2015; 108:251-60. [PMID: 25606674 DOI: 10.1016/j.bpj.2014.11.3462] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 11/11/2014] [Accepted: 11/19/2014] [Indexed: 02/07/2023] Open
Abstract
Total internal reflection fluorescence microscope has often been used to study the molecular mechanisms underlying vesicle exocytosis. However, the spatial occurrence of the fusion events within a single cell is not frequently explored due to the lack of sensitive and accurate computer-assisted programs to analyze large image data sets. Here, we have developed an image analysis platform for the nonbiased identification of different types of vesicle fusion events with high accuracy in different cell types. By performing spatiotemporal analysis of stimulus-evoked exocytosis in insulin-secreting INS-1 cells, we statistically prove that individual vesicle fusion events are clustered at hotspots. This spatial pattern disappears upon the disruption of either the actin or the microtubule network; this disruption also severely inhibits evoked exocytosis. By demonstrating that newcomer vesicles are delivered from the cell interior to the surface membrane for exocytosis, we highlight a previously unappreciated mechanism in which the cytoskeleton-dependent transportation of secretory vesicles organizes exocytosis hotspots in endocrine cells.
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6
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Forst AL, Olteanu VS, Mollet G, Wlodkowski T, Schaefer F, Dietrich A, Reiser J, Gudermann T, Mederos y Schnitzler M, Storch U. Podocyte Purinergic P2X4 Channels Are Mechanotransducers That Mediate Cytoskeletal Disorganization. J Am Soc Nephrol 2015; 27:848-62. [PMID: 26160898 DOI: 10.1681/asn.2014111144] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 06/10/2015] [Indexed: 11/03/2022] Open
Abstract
Podocytes are specialized, highly differentiated epithelial cells in the kidney glomerulus that are exposed to glomerular capillary pressure and possible increases in mechanical load. The proteins sensing mechanical forces in podocytes are unconfirmed, but the classic transient receptor potential channel 6 (TRPC6) interacting with the MEC-2 homolog podocin may form a mechanosensitive ion channel complex in podocytes. Here, we observed that podocytes respond to mechanical stimulation with increased intracellular calcium concentrations and increased inward cation currents. However, TRPC6-deficient podocytes responded in a manner similar to that of control podocytes, and mechanically induced currents were unaffected by genetic inactivation of TRPC1/3/6 or administration of the broad-range TRPC blocker SKF-96365. Instead, mechanically induced currents were significantly decreased by the specific P2X purinoceptor 4 (P2X4) blocker 5-BDBD. Moreover, mechanical P2X4 channel activation depended on cholesterol and podocin and was inhibited by stabilization of the actin cytoskeleton. Because P2X4 channels are not intrinsically mechanosensitive, we investigated whether podocytes release ATP upon mechanical stimulation using a fluorometric approach. Indeed, mechanically induced ATP release from podocytes was observed. Furthermore, 5-BDBD attenuated mechanically induced reorganization of the actin cytoskeleton. Altogether, our findings reveal a TRPC channel-independent role of P2X4 channels as mechanotransducers in podocytes.
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Affiliation(s)
- Anna-Lena Forst
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany
| | - Vlad Sorin Olteanu
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany
| | - Géraldine Mollet
- INSERM U1163, Laboratory of Hereditary Kidney Diseases, Imagine Institute, Paris, France
| | - Tanja Wlodkowski
- Division of Pediatric Nephrology, Heidelberg University Center for Pediatrics and Adolescent Medicine, Heidelberg, Germany
| | - Franz Schaefer
- Division of Pediatric Nephrology, Heidelberg University Center for Pediatrics and Adolescent Medicine, Heidelberg, Germany
| | - Alexander Dietrich
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany
| | - Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, Illinois; and
| | - Thomas Gudermann
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany; DZHK (German Centre for Cardiovascular Research), Munich Heart Alliance, Munich, Germany
| | - Michael Mederos y Schnitzler
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany; DZHK (German Centre for Cardiovascular Research), Munich Heart Alliance, Munich, Germany
| | - Ursula Storch
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany
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7
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Larson BT, Sochacki KA, Kindem JM, Taraska JW. Systematic spatial mapping of proteins at exocytic and endocytic structures. Mol Biol Cell 2014; 25:2084-93. [PMID: 24807904 PMCID: PMC4072581 DOI: 10.1091/mbc.e14-02-0771] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A quantitative cellular imaging and spatial mapping system is developed and used to measure a library of 78 proteins at calcium-regulated exocytic or clathrin-coated endocytic structures. Structures and proteins are randomly distributed. A steady-state network map is provided for studying the behavior of membrane-trafficking proteins. Vesicular secretion (exocytosis) involves the release and then compensatory recycling of vesicle components through endocytosis. This fundamental cellular process is controlled by the coordinated assembly and interactions of dozens of proteins at the plasma membrane. Understanding the molecular composition of individual exocytic and endocytic structures and their organization across the plasma membrane is critical to understanding the behavior and regulation of these two cellular processes. Here we develop a high-resolution and high-throughput fluorescence imaging–based approach for the unbiased mapping of 78 proteins at single exocytic vesicles and endocytic structures in neuroendocrine PC12 cells. This analysis uses two-color single-frame images to provide a systems-level map of the steady-state distributions of proteins at individual exocytic and endocytic structures in the cell. Along with this quantitative map, we find that both calcium-regulated exocytic vesicles (dense core vesicles) and endocytic structures (clathrin-coated structures) and the proteins associated with these structures exhibit a random spatial distribution in unstimulated neuroendocrine PC12 cells. This approach is broadly applicable for quantitatively mapping the molecular composition and spatial organization of discrete cellular processes with central molecular hubs.
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Affiliation(s)
- Ben T Larson
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Kem A Sochacki
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jonathan M Kindem
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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8
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Trouillon R, Ewing AG. Actin controls the vesicular fraction of dopamine released during extended kiss and run exocytosis. ACS Chem Biol 2014; 9:812-20. [PMID: 24400601 PMCID: PMC3985473 DOI: 10.1021/cb400665f] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
![]()
The effect of latrunculin A, an inhibitor
of actin cross-linking,
on exocytosis in PC12 cells was investigated with single cell amperometry.
This analysis strongly suggests that the actin cytoskeleton might
be involved in regulating exocytosis, especially by mediating the
constriction of the pore. In an extended kiss-and-run release mode,
actin could actually control the fraction of neurotransmitters released
by the vesicle. This scaffold appears to contribute, with the lipid
membrane and the protein machinery, to the closing dynamics of the
pore, in competition with other forces mediating the opening of the
exocytotic channel.
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Affiliation(s)
- Raphaël Trouillon
- Department
of Chemistry and Molecular Biology, University of Gothenburg, S-41296 Gothenburg, Sweden
| | - Andrew G. Ewing
- Department
of Chemistry and Molecular Biology, University of Gothenburg, S-41296 Gothenburg, Sweden
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, S-41296 Gothenburg, Sweden
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9
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Hissa B, Pontes B, Roma PMS, Alves AP, Rocha CD, Valverde TM, Aguiar PHN, Almeida FP, Guimarães AJ, Guatimosim C, Silva AM, Fernandes MC, Andrews NW, Viana NB, Mesquita ON, Agero U, Andrade LO. Membrane cholesterol removal changes mechanical properties of cells and induces secretion of a specific pool of lysosomes. PLoS One 2013; 8:e82988. [PMID: 24376622 PMCID: PMC3869752 DOI: 10.1371/journal.pone.0082988] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 10/29/2013] [Indexed: 11/18/2022] Open
Abstract
In a previous study we had shown that membrane cholesterol removal induced unregulated lysosomal exocytosis events leading to the depletion of lysosomes located at cell periphery. However, the mechanism by which cholesterol triggered these exocytic events had not been uncovered. In this study we investigated the importance of cholesterol in controlling mechanical properties of cells and its connection with lysosomal exocytosis. Tether extraction with optical tweezers and defocusing microscopy were used to assess cell dynamics in mouse fibroblasts. These assays showed that bending modulus and surface tension increased when cholesterol was extracted from fibroblasts plasma membrane upon incubation with MβCD, and that the membrane-cytoskeleton relaxation time increased at the beginning of MβCD treatment and decreased at the end. We also showed for the first time that the amplitude of membrane-cytoskeleton fluctuation decreased during cholesterol sequestration, showing that these cells become stiffer. These changes in membrane dynamics involved not only rearrangement of the actin cytoskeleton, but also de novo actin polymerization and stress fiber formation through Rho activation. We found that these mechanical changes observed after cholesterol sequestration were involved in triggering lysosomal exocytosis. Exocytosis occurred even in the absence of the lysosomal calcium sensor synaptotagmin VII, and was associated with actin polymerization induced by MβCD. Notably, exocytosis triggered by cholesterol removal led to the secretion of a unique population of lysosomes, different from the pool mobilized by actin depolymerizing drugs such as Latrunculin-A. These data support the existence of at least two different pools of lysosomes with different exocytosis dynamics, one of which is directly mobilized for plasma membrane fusion after cholesterol removal.
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Affiliation(s)
- Barbara Hissa
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Bruno Pontes
- LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Paula Magda S. Roma
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ana Paula Alves
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Carolina D. Rocha
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Thalita M. Valverde
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Pedro Henrique N. Aguiar
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Fernando P. Almeida
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Allan J. Guimarães
- Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Universidade Federal Fluminense, Rio de Janeiro, RJ, Brazil
| | - Cristina Guatimosim
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Aristóbolo M. Silva
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Maria C. Fernandes
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Norma W. Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Nathan B. Viana
- LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Oscar N. Mesquita
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ubirajara Agero
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Luciana O. Andrade
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
- * E-mail:
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10
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Trouillon R, Ewing AG. Amperometric measurements at cells support a role for dynamin in the dilation of the fusion pore during exocytosis. Chemphyschem 2013; 14:2295-301. [PMID: 23824748 PMCID: PMC3794367 DOI: 10.1002/cphc.201300319] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Indexed: 11/10/2022]
Abstract
Dynamin is a GTPase mechanochemical enzyme involved in the late steps of endocytosis, where it separates the endocytotic vesicle from the cell membrane. However, recent reports have emphasized its role in exocytosis. In this case, dynamin may contribute to the control of the exocytotic pore, thus suggesting a direct control on the efflux of neurotransmitters. Dynasore, a selective inhibitor of the GTPase activity of dynamin, was used to investigate the role of dynamin in exocytosis. Exocytosis was analyzed by amperometry, thus revealing that dynasore inhibits exocytosis in a dose-dependent manner. Analysis of the exocytotic peaks shows that the inhibition of the GTPase activity of dynamin leads to shorter, smaller events. This observation, together with the rapid effect of dynasore, suggests that the blocking of the GTPase induces the formation of a more narrow and short-lived fusion pore. These results suggest that the GTPase properties of dynamin are involved in the duration and kinetics of exocytotic release. Interestingly, and in strong contrast with its role in endocytosis, the mechanochemical properties of dynamin appear to contribute to the dilation and stability of the pore during exocytosis.
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Affiliation(s)
- Raphaël Trouillon
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden
| | - Andrew G. Ewing
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden
- Department of Chemical and Biological Engineering, Chalmers University of Technology, S-41296 Gothenburg, Sweden
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12
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Mace EM, Wu WW, Ho T, Mann SS, Hsu HT, Orange JS. NK cell lytic granules are highly motile at the immunological synapse and require F-actin for post-degranulation persistence. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2012; 189:4870-80. [PMID: 23066148 PMCID: PMC3558996 DOI: 10.4049/jimmunol.1201296] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The formation of a dynamic, actin-rich immunological synapse (IS) and the polarization of cytolytic granules toward target cells are essential to the cytotoxic function of NK cells. Following polarization, lytic granules navigate through the pervasive actin network at the IS to degranulate and secrete their toxic contents onto target cells. We examined lytic granule motility and persistence at the cell cortex of activated human NK cells, using high-resolution total internal reflection microscopy and highly quantitative analysis techniques. We illustrate that lytic granules are dynamic and observe substantial motility at the plane of the cell cortex prior to, but not after, degranulation. We also show that there is no significant change in granule motility in the presence of Latrunculin A (which induces actin depolymerization), when added after granule polarization, but that there is a significant decrease in lytic granule persistence subsequent to degranulation. Thus, we show that lytic granules are highly dynamic at the cytolytic human NK cell IS prior to degranulation and that the persistence of granules at the cortex following exocytosis requires the integrity of the synaptic actin network.
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Affiliation(s)
- Emily M. Mace
- Baylor College of Medicine, Houston, Texas, United States of America
| | - Winona W. Wu
- University of Pennsylvania College of Arts and Science, Philadelphia, Pennsylvania, United States of America
| | - Tina Ho
- University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Shaina S. Mann
- University of Pennsylvania College of Arts and Science, Philadelphia, Pennsylvania, United States of America
| | - Hsiang-Ting Hsu
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, USA
| | - Jordan S. Orange
- Baylor College of Medicine, Houston, Texas, United States of America
- Texas Children’s Hospital, Houston, Texas, United States of America
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